A semiconductor device fabricating process includes a fluid treatment that brings a process object, such as a semiconductor wafer, into contact with a processing fluid to treat the process object. In one example of the fluid treatment, the process object is immersed in a processing fluid, such as diluted hydrofluoric acid (DHF) or a rinse liquid, held in a cleaning tank in order to clean the process object. In another example of the fluid treatment, a mixed gaseous fluid of vaporized isopropyl alcohol (IPA) and nitrogen gas (N2 gas) is supplied to a process object to dry the same. In general, the temperature of the processing fluid must be regulated at a designated target temperature in order to achieve the desired process result. To this end, a fluid heating apparatus for regulating the temperature of the processing fluid is employed.
JP09-210577A discloses such a fluid heating apparatus. The fluid heating apparatus includes a heating lamp, a transparent quartz tube surrounding the heating lamp, and a tubular container surrounding the transparent quartz tube to define a fluid-flowing space between the transparent quartz tube and the tubular container. The fluid supplied into the fluid-flowing space through a fluid inlet flows through the fluid-flowing space, where the fluid is heated by the thermal radiation emitted from the heating lamp, and flows out of the fluid-flowing space through a fluid outlet. In this fluid heating apparatus, the fluid is exposed to the thermal radiation emitted from the heating lamp and transmitted through the transparent quartz tube so that the fluid absorbs the energy of the thermal radiation to be heated. To put it briefly, the fluid is “directly” heated by the thermal radiation.
In general, a fluid heating apparatus of the foregoing direct-heating type has some problems. First, if the thermal-radiation absorption of the fluid is high, the fluid flowing through an area, remote from the heating lamp, in the fluid-flowing space is not sufficiently heated, while the fluid flowing through an area, near the heating lamp, in the fluid-flowing space is efficiently heated. Thus, sufficient heating efficiency can not be achieved. If the fluid is a flammable or volatile organic solvent such as IPA, the fluid must be heated with particular attention on the temperature control.
The fluid heating apparatus of JP09-210577A is further provided with plural metallic fins for heating a fluid of low thermal-radiation absorption. The metallic fins are circumferentially arrayed in the fluid-flowing space and extend in the fluid-flowing direction. If the thermal-radiation absorption of the fluid is low, the thermal radiation emitted from the heating lamp falls on the metallic fins to heat the same. The fluid is heated by the heat transfer from the metallic fins to the fluid. The fin structure is complicated, and thus costly.
As mentioned above, in a fluid heating apparatus of the foregoing direct-heating type, the transparent tube surrounding the heating lamp is typically made of quartz. If the fluid to be heated is DHF, the quartz material contacting with the fluid will be dissolved therein, and thus cannot be used.